Understanding Hadron Structure through Electron-Positron Collisions

[maverick280857]

Hi,

Halzen and Martin, on page 18 of their book, describe the resolution of hadron structure using virtual photons obtained by annihilating e+ and e- beams.

In Figure 1.11(b), isn't the positron arrow shown wrongly? It seems to be moving forward in time. (Or maybe I'm just being picky here?)

They go on to say,

Colliding very high-energy electron and positron beams also provides us with an extremely "clean" technique to probe quarks (see Fig. 1.11b). The photon, produced at rest by e+ and e- beams colliding head on, can decay into a qqbar pair as shown in the pictuire.

What does "produced at rest" mean?

Thanks in advance!

 

[humanino]

In Figure 1.11(b), isn't the positron arrow shown wrongly? It seems to be moving forward in time. (Or maybe I'm just being picky here?)

It depends on one's convention, but it is inconsistent with their e+e- annihilation diagram 6.13

What does "produced at rest" mean?

It means it has no momentum in the lab.

 

[maverick280857]

It depends on one's convention, but it is inconsistent with their e+e- annihilation diagram 6.13
It means it has no momentum in the lab.

Thanks, I guess time runs vertically here.

 

[humanino]

Thanks, I guess time runs vertically here.

Actually I was confused. There is no inconsistency. Time always flows horizontally from left to right it seems. Also, it seems the arrow always points in the direction of positive energy.

 

[Hepth]

Nah, the problem is it's not a Feynman diagram, its a particle flow diagram. The arrows here basically correspond to particle flow. They're just trying to show that an e+ coming in and an e- coming in annihilate.